Electrophysiological experiments coupled with anatomical studies employing autoradiographic techniques are proposed to investigate the relationship between the midbrain raphe nuclei and the dorsal lateral geniculate of the cat. Physiological work will employ single unit recordings from geniculate neurons identified as sustained or transient coupled with electrical stimulation of the midbrain. We shall attempt to determine whether the inhibition of transient cells and the facilitation of sustained cells which follows midbrain stimulation is a function of one or more neurotransmitters. In addition, electrical stimulation of the lateral geniculate will be utilized in a study of antidromic activation of neurons in the midbrain raphe in order to obtain physiological confirmation of the anatomical studies. The anatomical work will involve injections of minute amounts of radioactive amino acid into the anterior portion of the dorsal raphe and the raphe intermedius to substantiate the existence of a pathway to the geniculate.